Avalanche Forecast
Issued: Feb 28th, 2018 4:14PM
The alpine rating is Wind Slabs and Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeStorm slabs on steep slopes, wind slabs on lee slopes, and a persistent slab that seems to be "waking up" on southerly slopes. There's lots to think about, and manage!
Summary
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
An approaching Low and associated weak front should only bring light snow Wednesday afternoon and overnight with winds backing to the south for the next couple of days.THURSDAY: Light snow with moderate east winds. Treeline temperatures around -5 to -10 CFRIDAY: More snow overnight Thursday and possibly into Friday with up to 10 or even 15 cm possible. However, there's significant uncertainty about the just how much new snow will fall. Having said that, highest amounts will be in the south, less as you go north towards Nakusp or Revelstoke. Light to moderate southerly winds.SATURDAY: trace to a few centimetres of snow, light and variable winds, treeline temperatures of around -10 C.
Avalanche Summary
Recent avalanche activity has consisted of mainly loose dry sluffing, storm slabs, or wind slabs (skier triggered and skier remote) in the size 1to 2 range. However, we've also received reports of persistent slab avalanches recent accumulations have been the highest. These avalanches, were remotely triggered (from a distance) or naturally occurring. We suspect the buried sun crust buried mid-February is the culprit with those on southerly aspects. Deep persistent avalanche activity has become less frequent over the past week.
Snowpack Summary
Around 20 to 40 cm of recent storm snow is being redistributed into deeper, reactive slabs in wind-exposed terrain. It also covers old surfaces including faceted powder, a sun crust on solar aspects, and surface hoar on shady slopes. Around 50 to 80cm below the surface there's a layer buried mid-February that's a sun crust on solar aspects, and spotty surface hoar on sheltered slopes. This layer looks most concerning on on solar aspects where it's associated with with small facets or surface hoar above. It also seems more of a problem in southern areas of the region.There are several deeper layers that have shown signs of improving but still remain suspect as low probability - high consequence avalanche problems. I'm talking about surface hoar layer buried back in December and January. Near the base of the snowpack is a November crust combined with loose sugary snow. These layers may "wake-up" with strong inputs such as sustained warming, sustained snowfall, large triggers (e.g. cornice fall, smaller avalanches coming down from above); human triggering is also possible in shallow, rocky terrain.
Problems
Wind Slabs
New snow and ongoing strong winds will continue to promote wind slab formation in wind-loaded areas on the leeward side of ridges and on cross-loaded slopes and gulleys. Storm slabs may also be found in sheltered area on steeper slopes and rolls.
Be cautious as you transition into wind affected terrain.Stay off recent wind loaded areas until the slope has had a chance to stabilize.Use caution on open slopes and convex rolls
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
An interface buried up to 70cm deep has "woken-up". This problem seems most reactive in south-facing terrain where buried crusts exist.
Choose conservative lines and watch for clues of instability.Carefully evaluate terrain features by digging and testing on adjacent, safe slopes. Carefully assess and consider avoiding southerly facing slopes.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 1st, 2018 2:00PM